Deities play an important part in most temples of Krishna. But what is the significance of Deities and Deity worship?
One thing to understand is that all the images or Deities in the Vedic pantheon, as found in the temples, are made according to explicit details and instructions found in the Vedic texts. Then they are installed in the temple in an elaborate ceremony wherein the Divine personalities are called to appear in the form of the Deity. Some of the Deities are demigods, while others, such as Krishna, Vishnu, or Ramachandra, are forms displaying various pastimes of the Supreme Being.
Some people, however, do not believe that God has a form. But many verses in the Puranas and particularly the Brahma-samhita establish that the Supreme Being does have specific forms according to His pastimes. These texts also describe His variegated features, which include His spiritual shape, characteristics, beauty, strength, intelligence, activities, etc. Therefore, it is considered that the authorized Deities of the Supreme that are shaped according to these descriptions provide a view of the personal form of God. God is described in the Vedic literature, which explains that God is sat-chit-ananda vigraha, or the form of complete spiritual essence, full of eternity, knowledge, and bliss, and is not material in any way. His body, soul, form, qualities, names, pastimes, etc., are all nondifferent and are of the same spiritual quality. This form of God is not an idol designed from someones imagination, but is the true form, even if He should descend into this material creation.
Some people may question that if the Deity is made from material elements, such as stone, marble, metal, wood, or paint, how can it be the spiritual form of God? The answer is given that since God is the source of all material and spiritual energies, material elements are also a form of God. Therefore, God can manifest as the Deity in the temple, though made of stone or other elements, since He can transform what is spiritual into material energy, and material energy back into spiritual energy. Thus, the Deity can easily be accepted as the Supreme since He can appear in any element as He chooses. In this way, even though we may be unqualified to see God, who is beyond the perceptibility of our material senses, the living beings in this material creation are allowed to see and approach the Supreme through His archa-vigraha form as the worshipable Deity in the temple. This is considered His causeless mercy on the materially conditioned living beings.
In this manner, the Supreme Being gives Himself to His devotees so they can become absorbed in serving, remembering and meditating on Him. Thus, the Supreme comes to dwell in the temple, and the temple becomes the spiritual abode on earth. In time, the body, mind and senses of the devotee become spiritualized by serving the Deity, and the Supreme becomes fully manifest to him or her. Worshiping the Deity of the Supreme and using ones senses in the process of bhakti-yoga, devotional service to the Supreme, provides a means for ones true essential spiritual nature to unfold.